The feasibility of a new electron microscopy technique, liquid scanning transmission electron microcopy (LiquidSTEM), will be assessed. LiquidSTEM has the potential to provide real-time imaging and analysis with high spatial resolution of dynamic biological processes in live specimens. Such capability could lead to completely new ways to study cellular processes on a molecular level, the discovery of new cellular phenomena and a deeper understanding of the many cellular processes currently being investigated by lower resolution imaging techniques. LiquidSTEM works by enclosing a biological sample in a flow cell that provides an environment to support cellular life directly within the electron microscope. A flow cell system is comprised of four main components: semiconductor devices and an adapter block to create a flowing liquid specimen chamber directly within the microscope, a specimen holder to provide a fluid interface from the semiconductor devices to the external environment, external liquid handling equipment and software. To demonstrate the feasibility of LiquidSTEM, a flow cell system will be designed and constructed and imaging conditions will be determined that allow a biological specimen to be kept alive during electron beam imaging. Semiconductor microfabrication techniques will be used to make the specimen chamber components and precision machining techniques will be used to make a specimen holder. Four key specific aims will be addressed to demonstrate feasibility: Design, construct and test a sealed flow cell with flowing liquid. Milestone: demonstration of fluid flowing through flow cell without leaks and without rupturing the membranes of the semiconductor devices. Design, construct and test a flow cell with calibrated flow rates. Milestone: calibration of flow rates with STEM imaging of gold nanoparticles flowing in the flow channel. Optimize the design, construction and operation of a flow cell for conditions to keep eukaryotic cells alive during imaging with an optical microscope. Milestone: observation of maintained expression of Green Fluorescent Protein (GFP) in Chinese Hamster Ovarian (CHO) cells. Optimize imaging conditions and buffers to keep eukaryotic cell alive during electron beam imaging, while providing molecular-level resolution on specific metal labels. Milestone: observation with STEM image of CHO cell with 30 nm resolution on nanoparticles and subsequent observation with optical imaging of GFP expression and fluorescence for several hours. A product will ultimately be developed to provide corporate and academic researchers with real-time imaging of dynamic biological processes with high spatial resolution in live specimens. LiquidSTEM will be performed with components added to a STEM, and thus, this new imaging capability will be compatible with existing and future STEMs.